A trocar-cannula is a surgical instrument. It can be used to drain fluid from a body cavity, introduce fluids into the body cavity, and insert a tool into the body cavity to perform surgical functions. The trocar-cannula is often comprised of two principal parts: (1) a hollow tube or cannula and (2) a puncturing member referred to as an obturator or trocar. The cannula is inserted through the wall of the body cavity with the assistance of the trocar passed through the cannula.
A trocar-cannula may be used in cardiovascular surgery, laparoscopic surgery, arthroscopic surgery, and intraocular surgery. In intraocular surgery, for example, a trocar-cannula is often used to obtain access to the posterior-segment of the eye (area behind the lens). Typically, a cannula is positioned on a needle of a trocar for insertion into the eye. The needle is used to penetrate the eye and insert the cannula. Upon insertion of the cannula, the trocar can be removed from the eye while the cannula remains inserted in the eye.